Purification of 1, 6-dinitronaphthalene and products therefrom



3,132,184 Patented May 5, 1964 s 132 184 PURIFICATION or ijs-ninrrnoNarnrnarunn AND rnonucrs THEREFROM Julius Hyman, Piedmont, Donald C. Morrison, Berkeley,

and Herbert P. C. Lee, Albany, Calif., assignors to Fundamental Research Company, Berkeley, Calif in partnership No Drawing. Filed May 4, 1961, Ser. No. 107,650

- ,13 Claims. (Cl. 260-645) v This invention relates to naphthalene chemistry. More particularly, it is concerned with the chemistry of certain dinitronaphtha-lenes, and, most specifically, with a process for the preparation of l,6- dinitronaphthalene from its admixture with 1,7 dinitronaphthalene and the products obtained in the carrying out of that process. 4

Pure l, 6-dinitrona3phthale ne has not hitherto been available commercially in spite of its great potential value as an intermediate in the preparation of many organic compounds, as, for example, steroids and other medicinals;

naphthalenediamines useful as anti-oxidants for rubber;

aminonaphthalene dyestuffs; and naphthalene diisocyanates, important reactants in the production of urethane fioams. 'A' need exists therefore for a method of preparing large quantities of 1,6-dinitronaphthalene inrelative'ly pure form at reasonable cost. The present invention provides such a method.

*A principal object of the invention is therefore a process for preparing 1,6-dinitronaphthalene in relatively pure form at reasonable cost.

A furtherobject of the invention is an elfective method of separating l,6-dinitronaphthalene in relatively pure form-fromits admixture with 1,7-dinitronaphthalene. Still=another object of the invention is a method of separating 1,6-dinitronaphthalene in relatiyely pure form from its admixture with 1,7-dinitronaphthalene, in which method the 1,7-dinitronaphthalene is converted into other naphthalene derivatives of value. The attainment of these and other objects of the'invention become apparent on further reading of this specification and the appended claims.

case the 1,7-isomer is converted by the reaction into soluble products, while the 1,6-isomer is substantially unaffected. The use of alkali metal alkoxide in methanol is generally preferred, since it converts the 1,7-isomer to the valuable 4,6-dinitro-l-naphthol and/or its methyl ether, or into 8-nitro-2-nitrosod-naphtho1 also called 8-ynitro- 1,ZnaphthQquinone-ZoXime), depending on the concen tration of the alkaline reagent employed. A- further advantage accruing from the use of the alkoxide is that the unaffected 1,-6-isomer is more readily washed free of impurities than when the other alkaline reagents mentioned are employed. When economical preparation and recovery of the 1,6-isomer is theprirnary consideration, however, the use of an aqueous solution of one of the water-soluble (and water-stable) alkaline reagents has its obvious advantages. I

We have found, in general, that the use of highly concentrated solutions of the alkaline reagents employed is not necessary, and, in some cases, may be actually destructive, particularly of the reaction" products of 1,-7-dinitronaphthalene. The permissible use of dilute solutions adds to the attractiveness of the process of our invention.

Because at the somewhat limited solubility of the mixture of 1,6- and 1,7'-isomers in methanol and ethanol, the

required volume of either of these solvents in a reaction stance, a mixture of lOO parts byweight-of methanol and .100 parts of benzene is sufiicient to dissolve the 6 parts of the mixed isomers, whereas if methanol alone were employed, at least 800 parts would be required. While the use of a co-solvent like benzene may add a procedural step, it results in considerable over-all economy in recovery costs.

While recovery of the reaction products of the 1,7

I isomer is important, the-process may be carried: out in A simple and greatly improved method of obtaining 1,6-

dinitronaphthalene in admixture with 1,7-isomer by dinitration of 2-nitronaphthalene is described in the copending application of Julius Hyman and Herbert P. C. Lee,

;S erial No. 1,427, filed January 11, 1960, now U.S. Patent T'No.f3,065,277. The product resulting from this dinitra- 'tion is a mixture of about percent each of 1,6-dinitronaphthalene and 1,7-dinitronaphthalene, with variations fup to about 1 0 percent depending on the particular conditions of preparation. From this mixture about one-sixth of the 1,6-isomer maybe recovered in relatively pure form from suchsolvents as methylene chloride, acetone or isopropano1; *the remaining dinitronaphthalene mixture, however, be resolved'only by gas or column chromato raphy methods which in the present state of the art do not lend themselves to commercial or industrial application.

We have nowfound that 1,6-dinitronaphthalenem1ay be "recovered. from such admixtures with the 1,7-isomer in alcoholic (in methanol or ethanol) solution of an alkali fmetalhydroxide'or (3) an aqueous-solution of an alkali 'nearlylql'lalntitative yields andin relatively pure form by reacting the mixture at moderate temperatures with a solution of proper concentration of an alkaline reagent which may be either (1) an alcoholic solution of an alkali imetal lalkoxide; e.g. sodium or potassium methoxide or ethoxide in methanol or ethanol respectively, or (2)" an metalhydroxide or carbonate or allcaline earth metal hydroxide, eg. sodium or potassium hydroxide or carbonate-or calcium or barium hydroxide, the choice of reagent in this-third group being dictated in part by its 'solubilityin the particular solvent concerned. 7 In either kip.

two steps, as is also described in Example 3.-

, Partial purification of the impure 1,6-dinitronaphthalene' separated from any of the reaction mixtures described may be effected in many cases by treatment with a solvent, such as acetone, in which the 1,6-isomer is soluble, and separating this solution from the insoluble matter by filtration, and evaporating the solvent from the (filtrate. In

our discovery of the sur rising and hitherto undiscovered sensitivity of 1,7-dinitr0naphthalene to attack by the ald-ifierence the behavior of the 1,6- and 1,7-isome rs kaline reagents described, and the immunity of the 1,6-

isomer to such attack. It is this completely unexpected which makes possible fior the first time an effective and substantiallyquantitati esepanation of 1,6 dinitrona} phthalene and, consequently, the practical production of this compound on a commercial scale. A substantial contribution to the knowledge of the chemistry of naphthalene is also made by this discovery; V a s The examples given below will illustrate in greater de- Three hundred parts by Weight of a mixture of 1,6- and 1,7-dinitronaphthalenes, in substantially equal proportail the principles and practice ofour invention, which is tions, obtained by'the dinitration of Z-nitronaphthalene according to the process of Hyman and Lee previously all of which are reaction products peatedly with cold 1,6-dinitronaphthalene and the referred to, were added to a solution of 100 parts of sodium methoxide in 2460 parts of methanol. This mixture was stirred for 6 hours at a temperature of about 55 C., after which it was cooled to about 30 C. and then vacuum filtered. T hesolids which remained on the filter were washed with 240 parts of cold methanol, fol lowed by 1,000 parts of water. The resulting cake was dried, and was found to consist of 125 parts of 1,6-di- 'nitronaphthalene with a purity in excess of 95 percent as determined by I-R spectrop'hotometric'analysis. The alkaline methanolic filtrates were Worked up for 4,6-dinitro-l-methoxynaphthalene and its corresponding naphthol, as well as for 8-nitro-l,2- naphthoquinone-Z-oxime,

of 1,7-dinitronaphthalene. Generally speaking, dilute methoxide solutions favor the production of the last-named derivative at the expense of the first, while prolonged reaction times tend to promote cleavage of the first-named derivative to form the corresponding naphthol. Temperatures much in excess of'about 45 to 55 C. are generally to be avoided,

tion of undesirable polymeric material.

If a higher purity 1,6-dinitronaphthalene is desired, the 7 product prepared as above may be refluxed for about 15 Example 2.Use of Sodium Ethoxide in Ethanol To two hundred parts by weight of ethanol there were added 2.0 parts of sodium metal to form sodium ethoxide, or sodium ethylate. When the reaction was complete, 10.0 parts by weight'ot a mixture of 1,6 and 1,7- "dinitronaphthalenes, obtained as specified in Example 1,

were added, and the resulting slurry was heated at 50- 5.5 C. for 18 hours. On cooling,

the slurry was filtered mixture was cooled to room temperature,

as such higher temperatures tend to pro-mote the forma- .solids were filtered off, was tracted with acetone, and the acetone solution then evapit After refluxing, the reaction filtered, and the solids washed and dried. An excellent yield (87 percent of theoretical) was obtained of to a 2 Normal solution.

photometric analysis.

Example 5 .Use of Aqueous NoOH Exomple 6.-Use of Aqueous Ca(OH) Five parts by weight of the same starting mixture of dinitronaphthalene used in the previous examples were refluxed with stirring for 96 hours in a mixture of 10 parts calcium hydroxide and 250 parts of water. The refluxed mixture was cooled to room temperature, the

bed with water, dried, ex-

' orated ofif. The residual solids consisted of 1,6-dinitrowithout dilution, and theresulting solids were washed rea water. These solids'were 1,6-dinitronaphthalene, with less than 5 percent of 1,7-dinitronaphthalene as an impurity. The recovery of solids was 4.0 parts by weight.

Example 3.Use of KOH in Methanol Six parts by weight of the same starting mixture of dinitronaphthalenes as employed in Example 1 were dissolved in 100 parts of benzene and then mixed with 100 parts of methanol. This mixture was cooled to 10 C., and a solution of 20 parts of potassium hydroxide in 60 parts of methanol added slowly with stirring. After standing 24 hours at ice bath temperature the mixture was introduced into an excess of ice water, whereupon two liquid layers formed. The benzene layer was separated and the solvent distilled off, leaving a mixture of ether formed from the reacted 1,7-dinitronaphthalene, this ether being 4,6-dinitro-l-methoxynaphthalene. This mixture was refluxed withstirring at about 100 C. for 2 hours with 5 percent aqueous KOH and yielded unchanged insoluble 1,6-dinitronaphthalene and an alkaline solution containing the potassium salt of 4,6-dinitro-1-naphthol. The reaction mixture was then cooled and filtered, and the separated 1,6-dinitronaphthalene washed with water and dried.

The alkaline filtrate was acidified with hydrochloric acid,

whereupon the dinitronaphthol was precipitated and was subsequently filtered oil, washed with water, and dried.

. Example 4.-Use of Aqueous KOH Ten parts by weight ofthe same starting mixture of V dinitronaphthalenes employed in the previous examples C. with 28 equivalent were refluxed for 1 hour with stirring at 100 parts potassium hydroxide in 250 parts water,

prime consideration, I nets of the alkali and 1,7-dinitronaphthalene of secondary in the scope of the invention as defined in naphthalene of a purity of percent as determined by I-R spectrophotometric analysis.

Example 7.Use of Aqueous Ba(0H) Ten parts by dinitronaphthalenes used in refluxed with stirring for 16 weight of the same starting mixture of the previous examples were hours with 200 parts of 0.25

Normal barium hydroxide solution. The refluxed solution was cooled to room temperature, the solids filtered off, Washed with water, dried, extracted with acetone, and

the acetone then evaporated oft".

ous alkaline solution isused at its reflux temperature,

approximately 100 C. In allof these cases the separation and recovery of the 1,6-dinitronaphthalene is the and recovery of the reaction prodor no importance.

From a consideration of the foregoing specification and examples it is evident that the basic process of our invention is susceptible to many modifications in detail which will naturally suggest themselves to one skilled in the art. Thus, for example, analogous alkaline compounds of the other alkali metals and alkaline earth metals may be used instead of those of the particular metals mentioned. Again, sodium carbonate and potassium carbonate may be utilized'instead of'the hydroxides, but the use of the carbonates is not preferred. Details of preparation may be changed in many respects in accordance with known procedures and techniques. All such modifications are deemed to be comprehended withthe claims.

We claim:

1. A process for treating a mixture of 1,6 and 1,7-

dinitronaphthalene whereby a substantial portion of the 1,7-constituent of the mixture is converted into reaction products which are readily separable from l,6-dinitroadmixture having the alkaline reagent constituent thereof at a concentration. level adequate to enable decomposition by said reagent of a substantial portion of said ,l,7-constituent, and maintaining saidadrnixture under a 1,6-dinitronaphthalene, with a purity of percent asdetermined by I-R spectrotemperature-time relationship adequate to enable said alkaline reagent to decompose said substantial portion of, said- 1,7-constituent.

2, The process of claim l-vvherein-said alkaline reagent is selected from the class consisting of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide.

. 3. A process according to claim 1 inwhich the mixture of 1,6-dinitronaphthalene and 1,7-dinitronaphthalene is dissolved in an inert solvent prior to the adding together reagent is potassium methoxide in solution in methanol.

8. Aprocess according to claim 2 in which the alkaline reagent is potassium ethoxide in solution in ethanol.

9. A process according to claim 1, the alkaline reagent being alkali metal hydroxide in solution'in methanol.

10. A process according to claim 1, the alkaline reagent being alkali metal hydroxide in solution in-methanol.

11. A process according to claim 1, the alkaline reagent 5 i being alkali metal hydroxide in aqueous solution.

7 12. A process. according to claim 1, the alkaline re-' agent being alkaline earth metal hydroxide in aqueous solution. v

13. A process for treating a mixture of 1,6- and 1,7- dinitronaphthalene whereby a substantial portion of the 1,7-constituent of the mixture is converted into reaction products which are readily separable from l,6-dinitro-.

naphthalene and wherin thelatter remains substantially unreacted comprising adding together said mixture and an alkaline reagent in solution selected from the class consisting of sodium methoxide dissolved in methanol,

sodium ethoxide dissolved in ethanol, potassium methoxide dissolved-in methanol, potassium ethoxide" dissolved in ethanol, sodium hydroxide dissolved in methanol, soium hydroxide dissolved in ethanol, potassium hyroxide dissolvedin methanol, potassium hydroxide dissolved in ethanol, sodium hydroxide in aqueous solution, potassium hydroxide in aqueous solution, calcium hydroxide in aqueous solution, and barium hydroxide in aqueous solution to form an admixture, said admixture having the alkaline reagent constituent thereof at a concentration level adequate to enable decomposition by said reagent of a substantial portion of said 1,7-constituent, and maintaining said admixture under a temperature-time relationship adequate to enable said alkaline reagent to decomposesaid substantial portion of said l,7 constituent.

No references cited. 

1. A PROCESS FOR TREATING A MIXTURE OF 1,6 AND 1,7DINITRONAPHTHALENE WHEREBY A SUBSTANTIAL PORTIN OF THE 1,7-CONSTITUENT OF THE MIXTURE IS CONVERTED INTO REACTION PRODUCTS WHICH ARE READILY SEPARABLE FROM 1,6-DINITRONAPHTHALENE AND WHEREIN THE LATTER REMAINS SUBSTANTIALLY UNREACTED COMPRISNG ADDING TOGETHER SAID MIXTURE AND A SOLUTION OF AN ALKALINE REAGENT OF THE CLASS CONSISTING OF ALKALI METAL ALKOXIDES, ALKALI METAL HYUDROXIDES, AND ALKALINE EARTH METAL HYDROXIDES TO FORM AN ADMIXTURE, SAID ADMIXTURE HAVING THE ALKALINE REAGENT CONSTITUENT THEREOF AT A CONCENTRATION LEVEL ADEQUATE TO ENABLE DECOMPOSITION BY SAID REAGENT OF A SUBSTANTIAL PORTIN OF SAID 1,7-CONSTITUENT, AND MAINTAINING SAID ADMIXTURE UNDER A TEMPERATURE-TIME RELATIONSHIP ADEQUATE TO ENABLE SAID ALKALINE REAGENT TO DECOMPOSE SAID SUBSTANTIAL PORTION OF SAID 1,7-CONSTITUENT 